The present invention is directed to a discharge machining apparatus and more particularly to improvements in such apparatus whereby accidents are prevented such as explosions caused by combustible gases produced from discharge machining which takes place in conjunction with a machining solution.
When discharge machining is carried out in the presence of a machining solution, it is a known fact that a sludge and combustible gases are produced. At the machining station where such discharge machining takes place the sludge and combustible gases thus produced will fill the machining station. The presence of the accumulated sludge will decrease the machining performance and an explosion of the combustible gases can damage the discharge machining apparatus.
In a conventional discharge machining apparatus of the type shown in FIG. 1, a machining station includes a tank 12 adapted to contain a machining solution, an overflow container 10 an electrode 14 and a device 16 for circulating a machining solution into and out of the tank 12. A machining anvil block 18 is placed on the upper end of the tank 12 and a workpiece 22 is fixed onto the upper surface of the block 18 over the hole 20 in alignment with the electrode 14 which is disposed above the block. The machining solution recirculation device 16 includes an exhaust pipe 24 for removing the solution from the tank 12 and an injection pipe 26 for supplying the solution into the tank 12.
In the operation of the conventional discharge machining apparatus of FIG. 1 the machining solution recirculation device 16 is operated as the electrode 14 approaches the workpiece 22 so that the machining solution is simultaneously withdrawn through the exhaust pipe 24 and supplied through the injection pipe 26. The recirculation device 16 is set so that the amount of machining solution withdrawn through the exhaust pipe 24 is greater than the amount of solution introduced into the tank 12 through the injection pipe 26 and additional machining solution is supplied through the gap between the electrode 14 and the workpiece 22 into the tank 10. During the subsequent discharge machining of the workpiece 22, sludge and combustible gases are produced but are withdrawn from the tank 12 through the exhaust pipe 24. In the conventional discharge machining apparatus disclosed in FIG. 1 it is difficult to adequately set the amounts of solution supplied and exhausted from tank 12 and accordingly, combustible gases tend to accumulate in the upper portion of the tank adjacent the exhaust pipe 24 whereby an accidental explosion of the combustible gases could cause damage to the apparatus.